The invention relates to a mobile crane with a main jib luffably mounted thereon and able to be raised via a luffing cylinder, and with a main jib extension releasably connected to a main jib head of the main jib via upper and lower bolts, the main jib extension, starting from a basic position after release of the upper or lower bolts, is able to be angled about a luffing axis relative to the main jib by means of an angling drive, the angling drive is a component of a combi-angling plate which delimits a maximum angling angle in a mechanically adjustable manner, wherein the angling drive engages on a foot of the main jib extension and the main jib head and the combi-angling plate consists of a sliding plate, a guiding plate and the angling drive.
The invention also relates to a method for angling a main jib extension relative to a main jib of a mobile crane.
German utility model DE 20 2004 020 760 U1 already discloses a mobile crane with a main jib and a main jib extension fastened to its main jib head. The main jib extension is luffable from a basic position, in which the main jib extension is orientated with its longitudinal direction as an extension of the longitudinal direction of the main jib, into a 20° position and a 40° position. In a conventional manner, the main jib extension is releasably fastened to the main jib head via two lower bolts disposed in the region of bottom chords of the main jib extension and two upper bolts disposed in the region of top chords of the main jib extension. In order to be able to luff the two lower bolts serving as a luffing axis out of the basic position, in a first step the two upper bolts are pulled and in a second step, by means of hydraulic luffing cylinders which engage on the main jib head and on the main jib extension, the luffing of the main jib extension is effected. The insertion and pulling of the two upper bolts is effected in each case via a hydraulic bolting cylinder. In order to power the luffing cylinders and the bolting cylinders an autonomous hydraulic assembly is disposed at the lower end of the main jib extension. It is possible to use e.g. a diesel engine or an electric motor, in each case with an associated hydraulic pump, as the hydraulic assembly.
The German patent DE 103 21 493 B4 discloses a mobile crane with a main jib extension and an angling plate. The angling plate is designed as a mechanically fixable telescoping device with a tubular guiding plate and a sliding plate which is guided and can be extended therein and which is likewise tubular. The guiding plate comprises stop openings for receiving bolts which ensure support of the sliding plate at its lower end and therefore permit a preselected length for the angling plate and therefore the angular adjustment of the main jib extension. The angling plate is disposed in the region of a bottom chord of the main jib and of the main jib extension. The desired angling is achieved by lifting the main jib, whereby the angling plate is shortened until the sliding plate contacts the bolts and is supported thereon.
Furthermore, European patent application EP 2 253 576 A1 discloses another embodiment of an angling plate for angling a main jib extension of mobile cranes. The angling plate formed from two angle levers comprises, in its basic position, which corresponds to a 0° position of the main jib extension to the main jib, a plurality of pairs of aligned stop openings for bolts. By selecting a pair of stop openings for the bolts the length of the angling plate can be varied and the main jib extension can be fixed in different angular positions, preferably 0°, 20° and 40°. The actual angling movement of the main jib extension is effected by means of a hoist located on the crane or next to the crane.